Identification and Characterization of Novel Transporters Involved in the CO2 Concentrating Mechanism of Chlamydomonas reinhardtii

The green alga Chlamydomonas reinhardtii possesses a CO2 concentrating mechanism (CCM) which helps in successful acclimation to low CO2 conditions. One of the main aspects of the CCM is bringing in inorganic carbon (Ci) into the cell as bicarbonate using Ci transporters. Current models of the CCM postulate that a series of ion transporters bring HCO3- from outside the cell to the thylakoid lumen where the carbonic anhydrase, CAH3, dehydrates accumulated HCO3- to CO2, raising the CO2 concentration for Rubisco. Previously, HCO3- transporters have been identified at both the plasma membrane (HLA3 and LCI1) and the chloroplast envelope (LCIA/NAR1.2), but the transporter thought to be on the thylakoid membrane has not been identified. The goal of this thesis has been to find the putative thylakoid transporter using a bioinformatics approach to identify candidate proteins followed by characterization of the interesting transporters using RNAi. Nine candidate proteins were identified from the Chlamydomonas proteome which had transporter like domains and were upregulated in low CO2. Three of the candidates are the paralogous genes (BST1, BST2, BST3) belonging to the bestrophin family, which are not only upregulated in low CO2 conditions but their expression is controlled by CIA5, a transcription factor known to control Ci transporters of the CCM. YFP fusions demonstrate that all three proteins are located on the thylakoid membrane and interactome studies indicate that they might associate with other chloroplast CCM components. A single mutant defective in BST3, still grows normally on low CO2, indicating that the three bestrophin-like proteins may have redundant functions. Therefore, an RNAi approach was adopted to reduce the expression of all three genes at once. RNAi mutants with reduced expression of BST1-3, were unable to grow at low CO2 concentrations, exhibited a reduced affinity for inorganic carbon compared to the wild type cells, and exhibited reduced inorganic carbon uptake. We propose that these bestrophin-like proteins are essential components of the CCM and deliver HCO3- accumulated in the chloroplast stroma to CAH3 inside the thylakoid lumen Another mutant , A144 was discovered to be a part of a large-scale mutagenesis project to select for mutants that have been transformed with a paromomycin cassette and grow slowly under low CO2 growth conditions. Using a modified form of the adapter PCR method, the location of the insert in A144 was found to be in a gene that codes for a protein with homology of fungal translational elongation factor (eEF3). This mutant cannot adapt to light after prolonged exposure to darkness and has a significantly lower rate of respiration than wild type. Thus we propose that EF3 putatively aids in the synthesis of stress proteins for dark adaptation

Religious Freedom Versus Gender Equity in Contemporary India: What Constitutions Can And Cannot Do

This article attempts to answer the question "Is religious freedom incompatible with gender justice in a multi-ethinic society?" by examining the processes of legal reform in India. The paper looks, in deatil, at contemporary debates about the role of the state in religion from the perspective of ensuring inalienable rights for women.Cet article tente de repondre a la question : « la liberte religieuse est-elle incompatible avec la justice pour les femmes dans une socidte multi-ethnique? » en etudiant le processus de la reforme judiciaire en Inde. Cet article etudie en detail les debats contemporains sur le rdle de 1'etat dans la religion, en partant de la perspective d'assurer des droit incommutables pour les femmes

Neutrino phenomenology and scalar Dark Matter with A4 flavor symmetry in Inverse and type II seesaw

AbstractWe present a TeV scale seesaw mechanism for exploring the dark matter and neutrino phenomenology in the light of recent neutrino and cosmology data. A different realization of the Inverse seesaw (ISS) mechanism with A4 flavor symmetry is being implemented as a leading contribution to the light neutrino mass matrix which usually gives rise to vanishing reactor mixing angle θ13. Using a non-diagonal form of Dirac neutrino mass matrix and 3σ values of mass square differences we parameterize the neutrino mass matrix in terms of Dirac Yukawa coupling “y”. We then use type II seesaw as a perturbation which turns out to be active to have a non-vanishing reactor mixing angle without much disturbing the other neutrino oscillation parameters. Then we constrain a common parameter space satisfying the non-zero θ13, Yukawa coupling and the relic abundance of dark matter. Contributions of neutrinoless double beta decay are also included for standard as well as non-standard interaction. This study may have relevance in future neutrino and Dark Matter experiments

How protein - Protein interactions contribute to pyrenoid formation in Chlamydomonas

© The Author(s) 2019. The chloroplast pyrenoid, an important component of the CO2 concentrating mechanism of algae, is a structure composed primarily of Rubisco. In Chlamydomonas, Rubisco in the pyrenoid is held together by the linker protein EPYC1. Atkinson et al., (2019) determined the regions of the Rubisco small subunit and EPYC1 that are important for the protein-protein interaction, thus making progress towards reconstruction of a pyrenoid in higher plants. Why is a protein soluble in one organism while its homologue in another species becomes part of a liquidlike cell structure? That is the question being addressed by Atkinson et al., (2019) in this issue of the Journal of Experimental Botany. It is even more striking when the protein is ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), the most abundant soluble enzyme in plants and algae. In terrestrial plants, Rubisco behaves as a soluble protein found throughout the chloroplast stroma of leaf mesophyll cells. However, in most algae, Rubisco is found in a structure within the chloroplast called the pyrenoid

Implications of the Dark-LMA solution for neutrino mass matrices

In this work we have re-investigated two different kinds of texture zero ansatz of the low energy neutrino mass matrix in view of the Dark-Large-Mixing-Angle (DLMA) solution of the solar neutrino problem which can arise in the presence of non-standard interactions. In particular we revisit the cases of (i) one zero mass matrices when the lowest neutrino mass is zero and (ii) one zero texture with a vanishing minor. In our study we find that for most of the cases, the texture zero conditions which are allowed for the LMA solution, are also allowed for the DLMA solution. However, we found two textures belonging to the case of one zero texture with a vanishing minor where LMA solution does not give a viable solution whereas DLMA solution does. We analyze all the possible texture zero cases belonging to these two kinds of texture zero structures in detail and present correlations between different parameters. We also present the predictions for the effective neutrino mass governing neutrino-less double beta decay for the allowed textures.Comment: 18 pages, 5 figures. To appear in Nucl. Phys.

Active and sterile neutrino phenomenology with A4A_4 based minimal extended seesaw

We study a model of neutrino within the framework of the minimal extended seesaw (MES), which plays an important role in active and sterile neutrino phenomenology in (3+1) scheme. The $A_4$ flavor symmetry is augmented by an additional $Z_4\times Z_3$ symmetry to constraint the Yukawa Lagrangian of the model. We use non-trivial Dirac mass matrix, with broken $\mu-\tau$ symmetry, as the origin of leptonic mixing. Interestingly, such a structure of mixing naturally leads to the non-zero reactor mixing angle $\theta_{13}$. Non-degenerate mass structure for right-handed neutrino $M_R$ is considered so that we can further extend our study to Leptogenesis. We have also considered three different cases for sterile neutrino mass, $M_S$ to check the viability of this model, within the allowed $3\sigma$ bound in this MES framework.Comment: V2; Accepted in Nuclear Physics